Herbicides are widely used to control weed growth in growing crop plants. Unchecked weed growth is detrimental to the crop plant because weeds compete with crop plants for light, water and various nutrients often resulting in lower crop yields as well as poorer crop quality. Compositions which protect the crop plant from the action of the herbicide, without reducing the herbicidal effectiveness against the weed to be controlled, are very beneficial.
Compounds which are useful in reducing or eliminating crop injury are variously referred to by those skilled in the art as antidotes, safeners or antagonistic agents. The substituted 2-imino-4-dihalomethylene-1,3-dithiolane derivatives described herein are useful as herbicidal safening agents as taught in U.S. Pat. No. 4,231,783, issued to the inventor herein.
Certain other 1,3-dithiolane derivatives, their use and processes for their preparation are known in the art; the following patents are representative of the art in this area.
U.S. Pat. No. 3,449,365 discloses 2-imino-4-alkalidene-1,3-dithiolanes and teaches that said compounds are useful as insecticides, acaricides and nematocides. U.S. Pat. No. 3,389,148 discloses processes for preparing substituted 1,3-dithioles,1,3-dithianes, and 1,3-dithiolanes and the salts thereof which are intermediates in the preparation of phosphorylated imino compounds. U.S. Pat. No. 3,189,429 and 3,139,439 disclose the preparation and herbicidal use of the halide salts of 2-dialkylamino-1,3-dithiolane derivatives. None of the above patents however teach the substituted 2-imino-4-dihalomethylene-1,3-dithiolane compounds described herein or their preparation via the photochemical cyclization process of the present invention.